Carpeting is manufactured from yarns or tows produced from natural or synthetic staple fibers or continuous synthetic filaments, respectively. The fibers are delivered to a yarn spinning plant in bales while the filament is shipped on cones. The yarn maker generally blends all of the staple fiber of a particular lot (generally 10 to 50 bales), through an opening process which consist of mixing portions of each bale in the lot in one or more opening operations (a process by which the compressed bale fibers are separated and by taking fibers from several bales at a time the fibers of the entire lot are blended, thus insuring a greater uniformity among the fibers, by carding as a first operation which tends to draw the fibers parallel and form long ropes of the fiber called card-slivers which are several inches in diameter). The output of these operations, the redistribution of the many fibers in the lot into a card-sliver, insures more uniform yarn properties, such as dye acceptance. In some instances the fibers are blended twice, or cross blended as this practice is referred to in the trade. Depending upon the ultimate use of the yarn, various treatments may be undertaken during blending, such as tinting for lot identification and/or application of lubricants and the like. The blended fibers in this rope-like card sliver are fed to pin drafters, an operation tending to further parallel the individual fibers and draw down the diameter of the resulting sliver. It is customary for the sliver to be pin-drafted several times so that the yarn (referred to as a singles) subsequently produced will be of the desired weight and, of course, obtain uniformity through further combining and paralleling of the fibers.
A yarn, or more properly a tow, may also consist of an assembly of any number of continuous mono-filaments drawn from several cones which are combined and twisted to give a continuous multi-filament tow singles.
Normally these singles yarns, from both staple and continuous filaments, are plied, two ply being the most common, by twisting the singles in a reverse direction to the singles twist, a process referred to as cabling.
In most modern day carpet mills the yarns or tows are "tufted" or punched through a scrim or primary backing made from jute, polypropylene or other woven or non-woven mmaterial on machines which may be and usually are computerized to enable numerous designs both as to length of the loop, type of loop, number of loops per inch, etc. to be made. This assembly can be, and usually is, dyed in one of the numerous batch or continuous dye machines commonly in use today. The so tufted carpet may have the loops cut, if a cut loop pile is desired, and an adhesive, such as latex, urethane or the like, applied and cured onto the back of the carpet to anchor the tufts to the primary backing. The carpet is usually trimmed to the desired width either at this point or before the latex is applied. To provide stability and weight to the carpet, a secondary backing of jute, polypropylene, or the like, may be attached to the back side of the carpet.
At the present time in order to produce reliable anti-static carpets for the most demanding uses, the electronics industry, it has become common practice for the carpet manufacturer to incorporate a metallic grid into the primary backing system. Such a technique is expensive and creates several problems for the manufacturer. The manufacturer must handle a heavy scrim which is less flexible than the ordinary scrim, and, because of the metallic grid, creates problems with the standard machinery used for tufting and handling carpet for dyeing, etc.
When the end use of the carpet is not to be placed under the severe criteria of the electronics industry, the mills have begun to blend or have blended into the staple fibers from which the yarn is spun a small amount of a conductive fiber to act as a static dissipation element. Such fibers are composites made conductive by incorporating into a hollow fiber a core of carbon (graphite) or by coating a fiber with a sheath made of a composite containing carbon (graphite), among the more common methods. These electroconductive fibers may be blended with the polymer fibers at the staple cutting stage. However, in many instances these composite fibers after, being made into staples, are added to the synthetic staple fibers at the opening stage. In most instances while electrostatic charges are dissipated to some degree when either of the afore described electroconductive fiber (sheath coated or hollow fiber filled with carbon (graphite) composites are employed only modest results are achieved.
It would therefore be advantageous for the consumer to have a more effective antistatic carpet. It would also be advantageous from the carpet manufacturers position to have a better conductor and a more readily incorporatable technique for placing the conductive fiber (carbon or graphite) into the existing carpet process to obtain a more uniform distribution and greater assurance that the contact with a substantial number of tufts, loop or pile of the carpet assembly are made to carry the static charge away from the source, i.e., distribute the charge over a large area of the carpet. In addition it would be advantageous for the manufacturer to eliminate the wire in the primary backing and thus eliminate the problems inherent therewith.